The present invention relates to a control gear for fluorescent lamps, which comprises two or more lamp circuits for igniting and burning fluorescent lamps, the lamp circuits comprising supply and igniting components specific for each lamp, and a supply line arranged to supply voltage to the lamp circuits.
Fluorescent lamps are generally used owing to their good lighting power. In addition, the long operating life of fluorescent lamps and the various tones of colour available enable their use in various applications.
A control gear is required for burning fluorescent lamps, the control gear supplying the ignition voltage necessary for the fluorescent lamp and the supply voltage necessary during its use. When using several fluorescent lamps connected to a prior art control gear, a problem arises from the fact that when one fluorescent lamp becomes defective, the fluorescent lamps connected to the same control gear cannot continue to function normally. Present control gears do not allow the switching off of a defective lamp without switching off the other lamps connected to the same control gear. This causes problems when lamps are replaced, because replacing one switched-off lamp does not necessarily allow the system to work.
It is an object of this invention to provide a control gear for fluorescent lamps, which avoids the above drawbacks and allows one and the same control gear to supply voltage to the fluorescent lamps in such a manner that the operation of one lamp is completely independent from that of the others. This object is achieved by a control gear of the invention characterized in that the control gear also comprises a switching element connected to a supply line and common to all lamp circuits, which element is arranged to cut the supply to all lamp circuits, switching elements specific for each lamp circuit, which elements are arranged to control the voltage of the lamps in the lamp circuits, a control unit arranged to control the common switching element and the switching elements specific for each lamp circuit, and lamp circuit-specific circuits for identifying a defective fluorescent lamp, which are arranged to transmit information on defective fluorescent lamps to the control unit.
The invention is based on the idea that an electronic control gear comprises, for each lamp, circuit switching elements with which the lamps can be controlled separately independent of the control of the other lamps. In normal operation, the switching elements of the lamp circuits are controlled in parallel using the same control. The control gear of the invention also comprises circuits for identifying defective lamps, and on the basis of the error information received from the circuits, the control of the defective lamp can be stopped, and the other fluorescent lamps connected to the same control gear can continue operation undisturbed. The control gear of the invention provides significant advantages with respect to condition control and maintenance of the lamps, since a defective lamp is easy to locate and replace when necessary.